Easiest way to get RED coins after today?

of course the Zero events (but I think those only give coins to the Zero). Not sure about anything farmable, but we'll see.

The coins you get from Zero actually come from boxes which are account tradeable, so you can get the 500 coins on any character(s) you want, as long as you transfer the boxes to your other character before you open them.

Anyone know if the Frozen E boxes give the same items as the Frozen R boxes? (were they in KMS?)

Items from the E boxes:
RED Coin
Equipment Enhancement Scroll
Mysterious Love Letter
Potions
Personality trait items
Summer Goggles (300 HP and MP, 2 attack and magic attack, expires)
Summer Goggles (200 HP and MP, 1 attack and magic attack, expires)
Summer Goggles (100 HP and MP, 1 attack and magic attack, expires)
Pink Flower Tubes